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diff --git a/guava/src/com/google/common/collect/PeekingIterator.java b/guava/src/com/google/common/collect/PeekingIterator.java
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+/*
+ * Copyright (C) 2008 The Guava Authors
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.google.common.collect;
+
+import com.google.common.annotations.GwtCompatible;
+
+import java.util.Iterator;
+import java.util.NoSuchElementException;
+
+/**
+ * An iterator that supports a one-element lookahead while iterating.
+ * 
+ * <p>See the Guava User Guide article on <a href=
+ * "http://code.google.com/p/guava-libraries/wiki/CollectionHelpersExplained#PeekingIterator">
+ * {@code PeekingIterator}</a>.
+ *
+ * @author Mick Killianey
+ * @since 2.0 (imported from Google Collections Library)
+ */
+@GwtCompatible
+public interface PeekingIterator<E> extends Iterator<E> {
+  /**
+   * Returns the next element in the iteration, without advancing the iteration.
+   *
+   * <p>Calls to {@code peek()} should not change the state of the iteration,
+   * except that it <i>may</i> prevent removal of the most recent element via
+   * {@link #remove()}.
+   *
+   * @throws NoSuchElementException if the iteration has no more elements
+   *     according to {@link #hasNext()}
+   */
+  E peek();
+
+  /**
+   * {@inheritDoc}
+   *
+   * <p>The objects returned by consecutive calls to {@link #peek()} then {@link
+   * #next()} are guaranteed to be equal to each other.
+   */
+  @Override
+  E next();
+
+  /**
+   * {@inheritDoc}
+   *
+   * <p>Implementations may or may not support removal when a call to {@link
+   * #peek()} has occurred since the most recent call to {@link #next()}.
+   *
+   * @throws IllegalStateException if there has been a call to {@link #peek()}
+   *     since the most recent call to {@link #next()} and this implementation
+   *     does not support this sequence of calls (optional)
+   */
+  @Override
+  void remove();
+}